Some judges in America have allowed the introduction of psychologists in court to help jurors understand eye-witness suggestibility – that is, how prone their memory is to distortion, for example by misleading questioning. But other judges have refused such expert testimony, on the basis that jurors ought to be able to rely on their common knowledge and intuition.

Now Bradley McAuliff and Margaret Kovera have put the issue to the test by taking a number of recognised factors from the research literature on suggestibility, and comparing the knowledge and understanding of these factors shown by 58 psychologist experts, 157 jurors and 220 undergrad students.

The psychologists correctly recognised that witnesses actively involved in an incident will be less prone to suggestion, as will witnesses questioned about central rather than peripheral details. The psychologists also recognised that misleading questions from a source lacking authority will be less damaging than such questioning from a source with some prestige. By contrast, the jurors and students failed to recognise the impact of any of these factors on witness suggestibility.

However, like the experts, the jurors and students did recognise that pre-school children will be more suggestible than young children and adults, although they underestimated the size of this difference. The jurors and students, like the experts, also realised that witnesses warned about the dangers of suggestion will be less prone to it, and that witness accuracy will be poorer, the longer ago a given incident occurred – no doubt because these factors really are common sense.

Ultimately, all the participants, experts and lay people alike, agreed that when it comes to witness suggestibility, expert testimony would be appropriate and helpful. “Certain information about witness suggestibility exceeds jurors’ common knowledge and understanding,” the researchers concluded._________________________________